Anatomy of Notary ctes typhlops. 83 



and which increases in size greatly and almost immediately, 

 occasions a pushing in of the ventral nasal furrow, the cavity of 

 which now becomes in cross-section foot-shaped, the inferior 

 septal ridge filling up the instep. Suddenly, just posterior 

 to this, there appears the swollen anterior end of Jacobson's 

 Organ (Fig. 3, J.O.^. The cartilage of the nasal floor may be 

 now called in part Jacobson's cartilage, since it has here lost its 

 connection with the nasal septum (Fig. 3, /.c^j. In this respect 

 Notoryctes resembles Ornithorhynchus^ and Echidna,* in which 

 Jacobson's cartilage "is continuous in front of the naso-palatine 

 foramen with the cartilage in the floor of the nose," as also with 

 the septum, "while behind it is separate." It resembles also the 

 Rabbit,^ and also the Guinea-pig,'' in that the cartilage is con- 

 tinuous with the cartilage of the nasal floor, though in each of 

 the latter the cartilage of Jacobson is altogether independent of 

 the cartilaginous nasal septum. The cartilage of Jacobson now 

 consists, on each side, of a crescentic shelf, from the middle of 

 the concavity of which rises, at right angles, a band of cartilage 

 (o.J.c), under which runs, near its anterior end, Jacobson's duct 

 (Fig. 3, J-d.) into the "toe" of the nasal furrow, while in the 

 groove formed between the band and the upper horn of the cres- 

 cent lies the Organ of Jacobson. In Notoryctes, the crescentic 

 cartilage of Jacobson is oblique, similar to that of Petaurus*, and 

 unlike that of Pseudochirus and Petauroides", which are more 

 vertical. 



The band or shelf of cartilage supporting the lateral wall of 

 Jacobson's Organ, is comparable in part to what is called the 

 septal turbinal in Macroscelides,' though arising from the main 

 cartilage at a diflTerent angle. It is further comparable to 

 Macroscelides in that this shelf is only connected with the 

 ventral cartilage behind the exit of Jacobson's duct from the 

 Organ, near its anterior end. This outer bar is similarly found 

 in most Marsupials, but that in Notoryctes differs from them in 



1 Proc. Zool. Soc, 1891, p. 578. 



2 Proc. Linn. Soc. N.S.W., vol. xi., n.s., 1896, p. 592. 



3 Q.J.M.S., vol. xxi., p. 550. 



4 Loc. cit., p. 220. 



5 Proc. Linn. Soc. N.S.W., vol. xi., n.s., 1896, p. 004. 



6 Loc. cit., p. 604. 



7 Proc. Zool. Soc, vol. i., pi. xxi., figs. 3 and 4, p. 226. 



